# Work done by a constant torque equation DOESN'T give me angular speed Help!

What is given:

Torque: τ = 34.5 N * m
Inertia: I = 0.130 kg * m2
Angular speed: ω = ?
Work done by a constant Torque: τΔθ = (1/2)Iωf2 [STRIKE]- (1/2)Iωi2[/STRIKE]
Angular displacement: Δθ = 17.1 rev/s = 107.442 rad/s

τΔθ = (1/2)Iωf2
(34.5)(107.442) = (0.5)(0.130)ωf2
3706.765 = 0.065ωf2
57027.156 = ωf2
238.8 = ω

It's still wrong :(

Last edited:

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Δθ is 17.1 revolutions. You need to convert that to radians.

Doc Al
Mentor

Doc Al
Mentor
3x should be enough

3x should be enough
Wait what? :(

I just did and it's still wrong

Doc Al
Mentor
I just did and it's still wrong
Show what you did.

If you show your work help may be given.

Show what you did.
B]What is given:[/B]

Torque: τ = 34.5 N * m
Inertia: I = 0.130 kg * m2
Angular speed: ω = ?
Work done by a constant Torque: τΔθ = (1/2)Iωf2 [STRIKE]- (1/2)Iωi2[/STRIKE]
Angular displacement: Δθ = 17.1 rev/s
Conversion (17.1 x 2 x π) rad/s = 107.442

τΔθ = (1/2)Iωf2
(34.5)(107.442) = (0.5)(0.130)ωf2
3706.765 = 0.065ωf2
57027.156 = ωf2
238.8 = ω

If you show your work help may be given.
But I just did

Doc Al
Mentor
Looks like they want the speed in rev/s, not rads/sec.

Looks like they want the speed in rev/s, not rads/sec.
Sooo...I don't convert angular displacement?

Doc Al
Mentor
Sooo...I don't convert angular displacement?

τΔθ = (1/2)Iωf2
(34.5)(107.442) = (0.5)(0.130)ωf2
3706.765 = 0.065ωf2
57027.156 = ωf2